The present invention relates to a method and apparatus for simulating portions of electrical circuits by using actual hardware components, such as integrated circuits, printed circuit boards and electrical circuit subsystems, in the simulation.
Heretofore, software systems have been developed for modeling or simulating the performance of circuit components. Through the use of software models, the design and engineering of electrical circuits is facilitated. Although these devices have proven to be powerful tools in aiding circuit designers, drawbacks exist, especially in software modeling of large-scale integrated and very-large-scale integrated circuit devices, such as microprocessors. For these latter devices, it is time-consuming and expensive to create software models. In this regard, the length of time required to prepare such models makes it difficult to create models as rapidly as new circuit designs evolve. Furthermore, complex software models are difficult to test and sometimes suffer from less than optimal reliability. Moreover, proprietary circuit designs are typically not subject to modeling unless the owner of the design releases sufficient information to enable the creation of a software model. Owners of circuit designs are frequently reluctant to provide such information.
In an attempt which partially addresses these problems, Daisy Systems and Valid Logic Systems, have developed devices designated respectively as "PMX" and "Real Chip". In each of these devices, a circuit designer uses a workstation equipped with software models of a number of circuit components. Each workstation is also connected to its own dedicated hardware component modeling unit. These hardware component modeling units contain actual integrated circuit components for use in modeling. When a user at a workstation is evaluating a circuit design having components corresponding to one or more of the hardware components in the hardware component modeling unit, the corresponding hardware component in the hardware modeling unit is accessed and is used for modeling. That is, test data is fed from the workstation to the physical component in the hardware modeling unit. Test results are then returned from the hardware modeling unit to the workstation following the test. In this way, an actual hardware component is used in modeling in lieu of a software model.
These existing devices suffer from a number of limitations. In the first place, as explained above, each workstation is associated with its own dedicated separate hardware modeling unit. Therefore, for example, four such workstations require four hardware modeling units. Consequently, to provide each user with access to a given integrated circuit for modeling, one of these integrated circuits must be provided in each of the hardware modeling devices. This can be prohibitively expensive. Moreover, it may be difficult or impossible in the case of proprietary circuits, where only one or a few such circuits are in existence.
The "PMX" and "Real Chip" devices also suffer from a variety of technical deficiencies. For example, they are understood to lack the capacity to clock the hardware components at very high speeds, required by some components to maintain them in an active condition, and lack other features which are desirable in circuit modeling systems.
Therefore, a need exists for an improved hardware modeling circuit system and method which is directed toward solving and minimizing these and other problems of prior art devices.